Current risk assessment tools have a moderate predicting value for violence. Their power may be enhanced with certain biological indicators, which may serve as predictors of recidivistic violence itself. The aim of our study was to determine the strength of serum insulin levels to predict violence, and compare these results with those from the Revised Psychopathy Checklist (PCL-R). The study population consisted of 105 Finnish alcoholics who were severely violent offenders, recruited from 1991 to 1998. After exclusion, 75 cases were followed until March 2008, or until a new offense was registered. Cox regression analysis was used to evaluate the risk of recidivism. The age and weight adjusted effect of insulin to recidivism risk showed a 7.2% increase for each International Unit (IU), or 19% for the mean difference (2.5IU) between recidivists and non-recidivist, which corresponds to a medium effect size (Cohen׳s d=0.46). Adjusting the insulin model with PCL-R factor 1 enhanced the predictive power slightly. Serum fasting insulin level was equivalent to the PCL-R factor 2 score as a predictor, and better than the total PCL-R score. However, the significance of these results was too low for predicting recidivism in the process of judicial decision-making.
Keywords: Alcoholism; Insulin; Psychopathy; Risk assessment; Violence.
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